1. Field of the Invention
The present invention relates to a method for efficiently removing saturated fatty acids from fatty acid mixtures.
2. Discussion of the Background
Fatty acids are widely used as intermediates for foods, such as monoglycerides and diglycerides, and as additives and intermediates for a variety of industrial products. Such fatty acids are generally produced by hydrolyzing vegetable oils, such as rapeseed oil or soybean oil, or animal fats, such as beef tallow, under high pressure.
However, the fatty acids produced by this method alone contain saturated fatty acids derived from the fats and oils used as the feedstock. Thus it has been found that these saturated fatty acids adversely influence final products such as monoglycerides and diglycerides. For example, when a fatty acid mixture containing saturated fatty acids is used as a feedstock to produce diglycerides, the diglycerides are in a semi-solid state at room temperature and, in cold districts or in the winter, completely crystallize (solidify) to lose their flowability. These diglycerides thus have poor appearance qualities and other problems, such as difficulty in removal from containers. Oleic acid has the lowest melting point among the fatty acids which are industrially mass-produced. However, even when oleic acid is used as a feedstock for diglycerides, the final product has a melting point of about 20.degree. C. and the above problems cannot be eliminated.